1. Field of the Invention
The present invention relates to a fuel hose, and more particularly, to a hose for transporting an automotive fuel, such as gasoline, alcohol-mixed gasoline, or diesel fuel.
2. Description of the Related Art
As a result of adoption of a direct injection engine and engine downsizing, there is a need for precise injection of a fuel. However, precise injection based only on electronic control of an injector has reached a limit, and there is a need for uniform transportation of the fuel, that is, a reduction in pulsation during fuel transportation.
In piping to be applied to a fuel supply system of an automobile, a fuel hose forms a passage for supplying a fuel to be pumped from a fuel pump, and is connected to a fuel delivery pipe. In such piping, the fuel is transported by pressurizing the fuel in the hose with the pump so as to have a preset constant pressure. In a system in which the fuel is supplied in divided portions to the engine with a plurality of fuel delivery apparatus, there is a risk in that pulsation (so-called fuel pressure variation) may be generated by one fuel delivery apparatus in the piping, which causes an excess or deficiency in pressure of the fuel in another fuel delivery apparatus, resulting in an error in amount of the fuel to be injected with respect to a desired amount. Accordingly, there is a need for a fuel hose configured to reduce the pulsation in the piping. In this context, it is conceivable to use a hitherto used fuel hose, such as a hose made of a resin, a hose made of a rubber, or a laminated hose of a resin and a rubber (see, for example, Japanese Patent Application Laid-open No. Hei 5-44874), but these hoses have the following problems.
That is, the hose made of a resin provides an effect of low fuel permeability (fuel barrier property), but has poor flexibility owing to its high rigidity, resulting in a poor pulsation-reducing effect. In addition, the hose made of a rubber provides a pulsation-reducing effect, but has a problem of being less satisfactory in terms of low fuel permeability (fuel barrier property). Further, in the laminated hose including a rubber and a resin layer serving as an inner layer, it is difficult to achieve both the low fuel permeability (fuel barrier property) and the pulsation-reducing property while keeping interlayer adhesiveness.
Therefore, hitherto, an approach to reducing the pulsation has involved, for example, using such fuel hose as described above in combination with a damping part, such as a pulsation damper (P/D), or increasing an overall length of the fuel hose.
However, the damping part, such as the pulsation damper (P/D), is expensive, and the increase in overall length of the fuel hose increases cost. Besides, such approach is not compatible with a need for a smaller engine room. Accordingly, there is a need for a novel method of coping with the problems. In addition, there is also a demand for performance such as calcium chloride resistance (resistance to a snow-melting agent) in a fuel hose for an automobile.